Originally Posted by zakco
In my experience XY imaging is not very wide to begin with and to my ears, sounds best hard panned. However, because the capsules are so close, this virtually eliminates phase issues when the two channels are panned in closer. You should have no problems narrowing them to taste. This is one of the advantages of XY.
Image width of XY is proportional to the angle between the mics. Wider angle - wider image. One can often see XY at 90° which for lots of applications is way too narrow. See also http://www.rycote.com/products/pdf/T...nic%20Zoom.pdf
Originally Posted by d_fu
XY being coincident, there will be no phase issues.
You can also reduce the L/R separation by simply reducing the angle between the capsules slighty.
I think what the original poster means is phase issues caused by bleed between two sets of XY mics, the piano pair also picking up drums.
If keeping to the 3:1 rule, ie the piano pair being at least 3 times farther from the drums than the drum pair, usually there won't be any issues. It's not always easy to stick to 3:1, especially on crowded stages.